1. Field of the Invention
The present invention relates to ducted fan aircraft. More particularly, the present invention relates to a system and method for controlling engine RPM of a ducted fan aircraft, such as, for example, a ducted fan vertical takeoff and landing (VTOL) aircraft.
2. Background Information
There have been numerous designs for vertical take off and landing (VTOL) aircraft that are powered by a single ducted fan. In such designs, the pitch, yaw and roll control moments are generated by vanes located aft of the fan, within the high-speed air flow. These vanes turn the exhaust flow about an appropriate axis to produce the required moments. In conventional designs, the vanes are grouped into two sets, each with their pivot axes perpendicular to each other and also perpendicular to the duct axis. The vanes are located either within the duct or just behind (e.g., aft of) the duct. Conventionally, one set of vanes produces pitch moments, and the other set produces yaw moments. Differential deflection of some or all of the vanes produces roll moments.
However, such designs suffer from numerous problems. For example, the vanes can only redirect a fraction of the total air flow for pitch or yaw control, thus limiting the maximum moments that can be produced. In addition, the vanes are in the high-speed air flow, which results in high drag and also block some of the nozzle area.